1. Field of the Invention
The invention disclosed herein relates to bi-directional communications between devices disposed in a drill string and a processing system disposed at the surface of the earth using an optical telemetry network.
2. Description of the Related Art
Exploration and production of hydrocarbons generally requires a borehole be drilled into earth formations, which may contain reservoirs of the hydrocarbons. To efficiently utilize drilling resources, many types of measurements are usually performed within the borehole.
The measurements can be of properties of the earth formations, properties of the borehole, properties of the fluid within the borehole, and a state of a drilling apparatus drilling the borehole. These measurements are often performed while the borehole is being drilled using sensors disposed at the drilling apparatus. Some of these measurements would be particularly useful to a drilling operator or a petro-analyst if they could be provided in real time. For example, knowledge of the earth formation being penetrated by the drilling apparatus can be used by the drilling operator to geosteer or guide the drilling apparatus in a more desirable path to more efficiently drill the borehole.
Unfortunately, it is difficult to transmit measurements to the surface of the earth in real time because of the harsh environment in the borehole and the dynamics of the drilling process. Similarly, transmitting information from the surface of the earth to sensors or devices disposed at the drilling apparatus downhole is also difficult.
Therefore, what are needed are techniques for communicating between devices disposed at a drilling apparatus downhole and the surface of the earth. Preferably, the techniques provide communications at times short enough to enable personnel at the surface of the earth to make timely drilling decisions and to maintain control of dowhhole instruments and devices.